It is known in the art relating to camshaft drives and the like to provide a variable timing means or phase changer to vary the angular orientation or phase of a camshaft relative to the crankshaft by which it is driven at a nominally fixed ratio, 1/2 crankshaft speed in four stroke cycle engines. The phase variation may be used for various purposes, such as to vary the valve timing to improve engine performance, economy or emission control.
It is also known in some engines to use the crankshaft or its drive to in turn drive other timed or non-timed accessories or devices, such as an ignition distributor, injection pump, oil pump or a balance shaft. In the latter case, at least, it is necessary to maintain a fixed speed ratio, such as 1:1 or 2:1, and a fixed phase angle between the crankshaft and the balance shaft so that desired engine balance may be maintained.
In a current engine having such a fixed ratio camshaft and balance shaft drive with a 1:1 balance shaft speed ratio, it was desired to provide means for varying camshaft phasing without altering the fixed drive ratio and phasing of the balance shaft which is driven by the camshaft drive. The resulting drive was to preferably require minimal change in the current drive arrangement and associated components.